Too much of a PITA Rated 3 out of 5 stars
Good in concept, but....
Whether this script provides an extra layer of security or not, IMO, it is a nagging PITA, which requires constant baby-sitting.
Yes, you can auto-allow bookmarks and with some surfing you can have it learn/allow your frequent sites...but anything else you surf, you will constantly be running to the button to temp allow just to gain functionality of many sites - which IMO, defeats the whole purpose of any added security benefit and makes normal surfing miserable.
If you knowingly frequent questionable sites such as porn or warez etc...this might be for you.
But like others have said, FF is already much safer than IE, I have a phishing filter and Norton Internet Security 2008 running in real-time with heuristics and firewall and a scheduled AV scan nightly.
When I weigh it out I'm safe enough without it and still have an enjoyable experience.